The present disclosure relates to a wheel hub drive having a planetary transmission, comprising a wheel hub, rotatably mounted on a fixed component, for receiving a tire with a gaseous filling and at least one fluid-carrying passage, which extends indirectly as far as the tire through the fixed component in order to regulate the gas pressure in the tire.
The area of application of the disclosure extends especially to motor vehicles, particularly preferably to off-road motor vehicles for agricultural use. During off-road operation, regulation of the gas pressure in the tires is desired in order to adapt the tire and the contact surface thereof to the respective underlying surface during movement. In the case of a loose underlying surface, e.g. mud, plowland, fields or snow, the gas pressure in the tires can be reduced in order to set a larger and more flexible contact surface of the tires. In the case of a hard underlying surface, e.g. asphalt, in contrast, the gas pressure in the tires can be increased in order to reduce rolling resistance and thereby reduce wear and consumption. The wheel hub is generally driven either hydrostatically or electrically. However, other drive options are also conceivable.
The publication EP 1 167 140 A2 discloses a wheel drive, particularly for mobile machines, having a supporting axle, which is attached to the vehicle frame in a manner fixed against rotation relative thereto and is rotatably connected by means of a rolling bearing arrangement to an annulus acting as a wheel hub. The annulus is driven by means of at least one planetary transmission having an input-side sun wheel, and an integrated dynamic service brake is provided between the annulus and the supporting axle. Within the annulus, the service brake is arranged directly behind a detachable transmission cover at the end and, radially on the outside, is arranged on a brake carrier in the form of a hollow cylinder forming the end piece of the non-rotatable supporting axle. As seen from the end, the planetary transmission is furthermore arranged behind the service brake within the annulus. The holding brake is actuated by means of the force of a brake spring, wherein the holding brake is held in the open position hydraulically via a pressure medium passage by means of the piston.
The publication DE 3 507 232 C2 discloses a wheel hub drive of compact construction having a planetary transmission. A wheel hub to be driven is rotatably mounted by means of rolling bearings on the end of an axle housing body. The planetary transmission for driving the wheel hub is arranged at the end of the axle housing body. The planetary transmission consists of a pinion shaft, which is guided through the axle housing body and has a sun wheel at its end, of a planet carrier housing, on which the planet wheels meshing with the sun wheel are mounted and which, for its own rotatable mounting and for motive power transmission, is connected to the wheel hub, and of an internally toothed annulus, which meshes with the planet wheels and is connected in a fixed manner to the axle housing body in order to transmit the reaction torque. For this purpose, use is made of a coupling wheel, which engages by means of an external toothing on the outer circumferential rim in the internal toothing of the annulus and is connected non-rotatably and detachably to the axle housing body. The releasable connection, transmitting the reaction torque, between the coupling wheel and the axle housing body consists in the coupling wheel and the axle housing body being designed at their mutually facing ends with matching inter-meshing teeth and the coupling wheel being rigidly flanged on at the end of the axle housing body.
The publication AT 391 298 B discloses a device for supplying and discharging compressed air to and from the pneumatic tires for motor vehicles having a wheel hub planetary transmission running gear assembly, having an air supply via a connection piece arranged in a bore in a shaft joint housing. The connection piece is connected via a bore in the shaft joint housing to a connection housing, which is closed by means of resilient seal rings and to which an axial bore in a half shaft guided by means of rolling bearings in the shaft joint housing is connected. Provided at the axially outer end of the half shaft is a centering guide bearing, the outer shell of which rests on the inner circumference of a connection cover provided with an air-carrying bore and designed as a cylindrical pot. A central spigot of the connection cover projecting axially inward from the connection cover is sealed off by means of a sealing collar and projects into a central receiving bore in the half shaft. The outer rim of the connection cover is connected to the end of the planet carrier of the wheel hub planetary transmission by way of a flexible insert.
The compressed air required to inflate the pneumatic tire is passed via a connection piece and through a bore in the shaft joint housing into a connection housing, which ensures loss-free transfer of the air to an axial bore in a half shaft with the aid of O-rings and radial shaft seal rings. The half shaft is passed through a rolling bearing from the connection housing side. To prevent oil from leaking through, a radial shaft seal ring is installed. The connection cover is connected to the manually actuated valve by a flexible line, thus allowing the air to flow into the interior of the pneumatic tire via a valve line. The tire pressure cannot be regulated during driving since there is only one fluid-carrying passage to regulate the tire pressure. The tire is mounted on a rim.
It is therefore the object of the present disclosure to provide a wheel hub drive having a planetary transmission, which drive is of compact construction and allows regulation of the tire pressure during driving.